<rant>You've got to be kidding me. If a potential employer handed me a test and said "You have 2.5 hours to complete this", I would walk out the door if I thought it would take me more than an hour. I have no qualms being verbally grilled and taking short written tests, but I would never take a 2.5 hour test.</rant>
I have performed several interviews and after talking with the person for 30-60 minutes I know what they know. My style of interviewing is a verbal test and discussion. It is very informal and allows for the answer to be presented in any way they feel comfortable (verbally, written, long explanation, or short answer).